Matrices, retainers and wedges /certified fixed orthodontic courses by Indian dental academy

MATRICES,
RETAINERS
AND WEDGES

INDIAN DENTAL ACADEMY
Leader in Continuing Dental Education

www.indiandentalacademy.com

MATRICES
• It was introduced in the year 1871 by Dr. Louis jack.

Definition
• Matrix is a device used to contour a restoration to simulate that of a tooth structure, which it is
replacing.
Or
• Matrix is a device used during restorative procedures to hold the plastic restorative material with in
the tooth while it is setting.

• MATRICING
• Is the procedure whereby a temporary wall is created opposite to axial walls, surrounding areas of
the tooth structure that were lost during the cavity preparation.

• IDEAL REQUIREMENTS OF A MATRIX
• Matrix should be inserted easily
• Should be sufficiently rigid to retain the contour given to it so that it can be transferred to the
restoration.
• Should not adhere or react with the restorative material
• Should resist the condensation pressure
• Ease of removal
• Economical

OBJECTIVES
• It must act as a temporary wall of resistance during introduction of the restorative material.
• It should provide shape to the restoration.
• Should confine the restoration with the acceptable physiological limits.
• It must assist in isolating the gingiva and rubber dam during introduction of restorative material.
• It must help in maintaining a dry operative field thereby preventing contamination of the
restoration.


PARTS OF A MATRIX
• Matrix system comprises of:
• Band
• Retainer.

MATRIX BAND

• Matrices are commonly supplied as strips of different dimensions.
• Thickness – may be 0.001” (0.025mm) or 0.002” (0.05mm)
• Width – may be ¼”, 3/8”, 5/16” or 1/8”.
• Depending on the height of the restoration, suitable matrix band is selected.

Materials used are:
• Stainless steel
• Cellulose acetate (cellophane)
• Cellulose nitrate(celluloid)
• Polyacetate (mylar)
• Copper band

Matrices are also supplied as
• crown forms
• split crown forms
• hollow cylinders
• curved bands with one or more cervical extensions

RETAINER
• This is a device by which the band can be maintained in its designated position and shape. The
retainer may be a mechanical device , dental floss, a metal ring or impression compound.


CLASSIFICATION OF MATRICES
Classified in different ways:

• Based on mode of retention
• Based on type of band material
• Based on its preparation
• Based on the cavity preparation for which it is used
• Based on transparency

I.Based on mode of retention
• With retainer
Eg. Tofflemire, ivory no. 1 & ivory no. 8 matrices
• Without retainer
Eg. Automatrix

II.Based on type of band material
• Stainless steel
• Cellulose acetate (cellophane)
• Cellulose nitrate(celluloid)
• Polyacetate (mylar)
• Copper band

III. Based on its preparation
• Custom made or anatomic matrix
Eg. Compound supported matrix
• Mechanical matrix
Eg. Tofflemire, ivory no. 1 & ivory no. 8 matrices

IV. Based on the cavity preparation for which it is used

• Class I cavity with buccal or lingual extension

Eg double banded tofflemire matrix

• Class II cavity
Single- banded tofflemire matrix,
Ivory no. 1 & ivory no. 8 matrices,
Compound-supported matrix,
Copper band matrix,
T- band matrix ,
Pre-contoured sectional matrix,
Automatrix.

• Class III cavity
S-shaped matrix,
Cellophane strips,
Mylar strips

• Class IV cavity
Cellophane strips,
Transparent celluloid crown forms,
Dead soft metal matrix strips.

• Class V cavity
Window matrix,
Tin foil matrix,
Pre formed transparent cervical matrix

V. Based on transparency
• Non transparent matrices
• Transparent matrices

DESCRIPTION OF VARIOUS MATRICES

I. IVORY NO.1 MATRIX

• Consists of a stainless steel band which encircles one proximal surface of a posterior tooth. This is
attached to the retainer via a wedge shaped projection. An adjusting screw at the end of the
retainer adapts the band to the proximal contour of the prepared tooth . as the adjusting screw is
rotated clock-wise the wedge shaped projections engage tooth at the embrasures of the
unprepared proximal surface.

• Indications
• Unilateral class II cavity especially when the contact on the unprepared side is very tight.
•

II. IVORY NO.8 MATRIX

• Consists of a band that encircles the entire crown of the tooth.
• The circumference of the band can be adjusted by adjusting the
screw present in the retainer.
• Indications

III. TOFFLEMIRE UNIVERSAL DENTAL MATRIX BAND RETAINER :

• Devised by Dr. B.F.Tofflemire .
• This is the most recent development, presenting a number of advantages.

• Indications
• For class I cavities with buccal or lingual extensions
• For restoring class II cavities on one or both proximal surfaces of a posterior tooth.

• Advantages
• Ease of use .
• Rigid and stable
• Produces good contact and contour for most amalgam restorations.

• Disadvantages
• Does not provide optimum contour and contact for posterior composite restorations.
• Not useful for extensive class II restorations

• Parts :
• HEAD : This accommodates the matrix band. It is U-shaped with 2 slots. The open side
of the head should be held facing upwards when the band is inserted and while
positioning the band around the tooth the slots in the head should be directed gingivally.
The head may be straight or angulated with respect to the rest of the retainer.
Accordingly there are 2 types of tofflemire retainers:
– Straight tofflemire retainer: here the head is straight. This can be positioned only
from the buccal side.
– Contra-angled tofflemire retainer: Here the head is angled and this can be placed
either from buccal or lingual side.


• LOCKING VISE: This has a diagonal slot. It is positioned near the head for placing the band in
the retainer and positioning it around the tooth.
• POINTED SPINDLE: This is used to adjust the distance between the head and the locking vise and
also to adjust the size of the loop of the matrix band.
• SMALL KNURLED NUT: Turning this nut clockwise tightens the pointed spindle against the band
and thus secures the band in the retainer. The reverse motion releases the pointed spindle from
the locking vise thus releasing the band from the retainer.

– LARGE KNURLED NUT : This is used to adjust the size of the loop of the matrix band either to
adapt it tightly against the tooth or to loosen it from the tooth.

• Tofflemire retainers are available in 2 sizes :
– Standard –for use in the adult dentition
– Small - for use in the primary dentition


Burnishing matrix band. a. With band on the pad using a small burnisher. b. smoothening using a large burnisher.
c. burnished matrix ready for use in MOD tooth preparation


IV. COMPOUND SUPPORTED MATRIX

• Also called the custom made matrix or anatomical matrix.
• It is entirely hand-made and is contoured specifically for individual cases.
• Uses a 5/16th inch wide, 0.002” thick stainless steel band cut to a sufficient length so that it wraps
around 1/3rd of the facial and lingual surface beyond the prepared proximal surface.
• The band is contoured with an egg-shaped burnisher on a paper pad to achieve the appropriate proximal
as well as facial and lingual contours of the prepared tooth.
• The band is placed in position and wedged. Following this the band is stabilized by applying softened
impression compound facially, lingually and occlusally over the occlusal surface of the adjacent tooth.
• The contour of the compound supported matrix may be improved by applying a warm burnisher against
the band within the prepared cavity
• Following this amalgam condensation and carving can be done.
• To remove the matrix, the compound can be broken away with a sharp explorer and the matrix strip can
be removed.
• Indications
• For restoring class II cavities involving one or both the proximal surfaces.
• For complex situations like pin retained amalgam restorations

• Advantages
• Highly rigid and stable
• Provides good access and visibility for placing the restorations
• More efficient means of reproducing contact and contour.

• Disadvantages
• Time consuming


V. T-BAND MATRIX

• This is a preformed t-shaped stainless steel matrix band without a retainer.
• The long arm of the ‘T’ is bent or curled to surround the tooth circumferentially. This overlaps the
short horizontal arm of the ‘T’ which is then bent over the long arm and thus helps to retain the
shape.
• The band is adjusted according to the circumference of the tooth, stabilized by wedging and
supported with low fusing compound.

• Indications
• For restoring class II cavities involving one or both the proximal surfaces of a posterior tooth.

• Advantages
• Simple and inexpensive matrix system
• Rapid and easy to apply.

• Disadvantages
• Flimsy in structure, not very stable.

VI. PRECONTOURED MATRIX

• Consists of small, precontoured dead soft metal matrices ready for application to the tooth.
• They are selected according to the tooth to be restored and wedged to adapt to the gingival
contour.
• Following this the band is held in place by a flexible metal ring called BiTine ring.
• The metal ring holds the ends of the matrix band snugly against the facial and lingual enamel. Eg.
Palodent bitine matrix system, composi-tight matrix system.

• Indications
• For restoring small class II cavities
involving one or both the proximal
surfaces of a posterior tooth.
• For both amalgam and composite
restorations

• Advantages
• Ease of application.
• The metal ring also affords slight tooth separation.
• Provides better proximal contours for posterior composite restorations than traditional matrices.

• Disadvantages
• Expensive
• Matrix bands may become dented easily especially if the contact area of the adjacent tooth is too
close preventing easy insertion of the band.

VII. COPPER BAND MATRIX

• These are cylindrical in shape and can be selected according to the diameter of the tooth to be
restored.
• The bands are softened by heating to redness in a flame and quenching in water.
• After this the bands can be stretched and shaped with contouring pliers. The band is festooned in
the cervical aspect with curved scissors so as to fit the gingival contour of the tooth.
• The occlusal height of the band is also adjusted. With contouring pliers the band is contoured to
reproduce the proper shape of the contact area and the buccal and lingual contours.
• Areas of the band in the contact area are thinned using a green stone.
• Following this the band is seated on the tooth and the gingival border is crimped inward to seal off
the gingival margins.
• Using a heated ball burnisher from the inside of the cavity to the band, contours can be improved.
• After condensation and carving o the amalgam, the band is left in place.it is sectioned and removed
at the next appointment.

• Indications
• For badly broken down teeth especially those receiving pin amalgam restorations.
• For complex situations like class II cavities with large buccal or lingual extensions.

• Advantages
• Provides excellent contour

• Disadvantages
• Time consuming www.indiandentalacademy.com

• VIII. AUTOMATRIX
• It is a retainerless matrix system.

Has the following components:
• AUTOMATRIX BANDS : Available in thickness of 0.0015 to 0.002 inch.
They may be of 3 widths :
• Narrow -3/16th inch
• Medium – ¼th inch
• Wide – 5/6th inch
• They may be selected according to the height of the tooth to be restored.

• AUTOMATE II TIGHTENING DEVICE
• This is used to adjust the loop of the band according to the circumference of the tooth to be
restored.

• SHIELDED NIPPERS
• This device is used to cut the autolock loop so that the band can be separated and removed from
the tooth after the restoration is done.


• Indications
• For complex amalgam restorations especially when one or more cusps are to be replaced.

• Advantages
• Convenient to use.
• Improved visibility due to lack of interference from a retainer.
• Autolock loop can be positioned facially or lingually.
• Rapid application.

• Disadvantages
• Bands are flat and difficult to burnish.
• Cannot develop proper proximal contacts and contours.
• Expensive

IX. CLEAR PLASTIC MATRIX

• Transparent plastic strips are employed as matrices for tooth-coloured restorations as they allow
light to be transmitted during polymerization of composite resins. These may be cellophane or
mylar strips, which may be contoured using operating pliers.
• The convex contoured area of the matrix band is positioned facing the proximal surface of the tooth
to be restored. The band should extend at least 1mm beyond the gingival and incisal margins of the
cavity preparations.
• It can be stabilized by a wooden or light transmitting wedge.
• After inserting the composite resin material the matrix is pulled tightly around the tooth following
which light curing is done.once the restoration is completed, the wedge can be removed and the
matrix strip slid out of the proximal surfaces of the contacting tooth.

• Indications
• For small and large class III and class IV tooth-colored restorations.

• Advantages
• Easy to use
• Inexpensive

X. TRANSPARENT PLASTIC CROWN FORM MATRIX

• These are commercially available transparent plastic crown forms. They are available in various
sizes and contours for anterior teeth.
• A suitable crown form can be selected for the prepared tooth and trimmed to fit 1mm past the
prepared margins. Since it is thicker than a clear plastic matrix strip, the contact area in the crown
from should be thinned with an abrasive disk so that once the matrix is removed the restoration
contacts the adjacent tooth.
• The bulk of the composite resin is loaded into the crown form. This is then positioned over the
crown form. This is then positioned over the tooth and light curing is done. Thus the contours of the
tooth can be shaped easily. After curing the crown form can be slit with a bur and removed.

• Indications
• For large class IV cavities.
• For oblique fractures of the anterior teeth.

• Advantages
• Easy to use.
• Good contours can be established.

• Disadvantages
• Placement is time consuming
• Expensive

XI. S-SHAPED BAND

• This is a metal matrix band moulded into an S-shape by contouring. After the band is positioned
and contoured over the contacting teeth, it is stabilized using wedges and impression compound.

• Indications
• For class III restorations on the distal surface of the canines.
• For class II slot restorations

• Advantages
• www.indiandentalacademy.com
Provides ideal contour for class III restoration on the distal surface of canines.

XII. WINDOW MATRIX

• This is a modification of the tofflemire matrix. It is used for class V restorations. The contra-angled
tofflemire retainer is applied on the lingual side of the tooth. A window is cut in the band slightly
smaller than the outline of the cavity.
• Wedges are placed interproximally to stabilize the band. Following this amalgam can be condensed
through the window and contoured using carvers. The matrix is removed once the amalgam has
hardened.

XIII. TIN FOIL MATRIX

• Used for class V restorations for conventional glass ionomer cements.
• Tin foil may be preshaped and cut according to the gingival third of the buccal and lingual surfaces of
the teeth to be restored.
• The band is adjusted so that it extends 1 or 2 mm circumferentially beyond the cavity margins. This
can be adapted on the cavity by means of a tweezer after placing the GIC . once the restoration sets
the tin foil matrix can be peeled away.

• Indications
• For class V restorations with conventional GIC.

• Advantages
• Simple and easy to use.
• Provides optimum contour for the restoration.

• Disadvantages
• Not useful for class V composite resin or resin modified GIC restorations.

XIV. PREFORMED TRANSPARENT CERVICAL MATRIX

• Used in anterior and posterior teeth.
• They are designed for use with light cured composite resins or GIC’s
• A tweezer or a handle can hold the matrix in place while the restoration is hardening.

•
•
Indications www.indiandentalacademy.com
For class V restorations with composites or resin modified GI restorations.

• Advantages
• Provides good contour for the restoration.

• Disadvantage
• Expensive

WEDGES
• Third component of the matrix system
• Wedging provides rapid or immediate separation. The separation achieved is based on the wedging
principle.

• Wedging serves the following purposes :
• Prevents surplus amalgam being forced into the gingival crevice.
• Assists in contouring the cervical part of the proximal surface.
• Separates the teeth to compensate for the thickness of the matrix band such that proximal contact
is re-established when the band is removed.
• Stabilizes the matrix.

Wedges are made of
• Wood,
• Plastic or celluloid,
• Metal,
• Silver,
• Medicated wooden wedges .

Wooden wedges are preferred because :
• They are easy to trim with a scalpel and they adapt well to the tooth surface.
• When properly shaped they remain stable during condensation.
• Also absorb moisture and swell to provide adequate stabilization.
•
Wooden wedges can be cut from toothpicks.

SHAPES
• Cross-section of the wedges are:
• Triangular
• Round.

• LIGHT TRANSMITTING WEDGES:
• These are plastic wedges that are transparent and have a light reflecting core.
• Used with transparent matrices while placing class II composite restorations.
• These can transmit 90 to 95% of the incident light, drawing the curing light to the gingival margin
of the restoration thus directing the polymerization shrinkage towards the margin.
• They provide better marginal adaptation at the cervical area of class II composite resin
restorations.


PLACEMENT AND LOCATION OF WEDGES

• Correct location is in the gingival embrasure just beneath the contact area.
• Wedge can be inserted buccally or lingually. It depends on cavity preparation and placement of the
band. Location of the retainer dictates the direction of insertion.
• Generally, wedge is inserted from the lingual side as this embrasure is larger in size. In lower arch
as lingual wedge interferes with the tongue, it is placed from the buccal side. In upper arch it is
placed from the palatal aspect.
• Wedging should not be done from both the sides as it might leave large space just below the
contact area leading to overhanging of the amalgam at that area.
• Length of the wedge should be only ½” or 1.3cm so that it does not irritate the tongue or the
cheek.
• Care should be taken to ensure that the wedge is positioned apically in relation to the gingival
cavity wall.
• The gingival wedge should be tight enough to prevent overhanging of the restoration.


SPECIAL WEDGING TECHNIQUES

• PIGGY BACK WEDGING

• If the wedge is significantly apical of the gingival margin, as in gingival recession in
the interproximal area and the proximal box is shallow gingivally, then a second, usually smaller
wedge may be ‘piggy-backed’ on the first wedge

• DOUBLE WEDGING

• In this technique, two wedges are used one from the buccal side and other from the lingual
aspect to provide close adaptation of the matrix at the cervical aspect of the tooth.
• Indicated when the proximal box is wide in the buccolingual dimension or in case of spacing
between the teeth.

• WEDGE-WEDGING

• Mostly employed on the mesial aspect of maxillary 1st premolars. Since these teeth have fluted
areas (concave) in the root near the gingival margin, placing a single wedge may still leave an
open margin gingivally.
• Therefore a second wedge can be inserted between the first wedge and the band so that this
opening is eliminated and the matrix band is well adapted to the gingival margin of the prepared
cavity.


• References

• Text book of operative dentistry : ramyaraghu
• Text book of operative dentistry : vimal.k. sikri
• Operative dentistry : sturdevant


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